Design,Synthesis And Application Of Amphiphilic Cyclic Polymer

At present,cyclic polymers with topological structure have been a hot topic in the research of polymers.They have many special properties compared with the linear polymers.Cyclic topological structure can improve the thermal and chemical stability and decrease the hydrodynamic volume of polymer.Biomedical tissue engineering materials from the linear polymers always have smooth surface and poor biocompatibility,which could cause tissue reaction severely.For topological structure polymer materials,there are spongy and fibrous structures on the surface,so they perform better biocompatibility.Thus,the cyclic topological structure polymer could be widely used in the nanotechnology,biomedicine and other fields.However,the synthesis of cyclic polymer is complicated and the reactivity of end functional groups is low.So it is a great challenge to synthesize cyclic polymer.Combination of atom transfer radical polymerization(ATRP)and Cu(?)-catalyzed cycloaddition of alkynes and azides(CuAAC)could solve these problems easily because of the high reactivity of living radical polymerization and high selectivity of"click" chemistry.And it is also a really popular method in the systhesis of cyclic polymer.In this paper,the content of research mainly includes:In the chapter one,we introduced the structure,properties and synthetic methods of cyclic polymer briefly.Several synthetic methods of cyclic polymer combining living polymerization and "click" chemistry were described in detail.Among these methods,the combination of atom transfer radical polymerization(ATRP)and Cu(I)-catalyzed cycloaddition of alkynes and azides(CuAAC)has wider applications,higher yield and the simplest experimental operation.Then we further to elucidate about preparation methods and research status of amphiphilic cyclic polymer micelles.In the chapter two,the amphiphilic cyclic poly(?-caprolactone-b-(N-vinylpyrrolidone))copolymer(cyclic-PCL-b-PVP)was synthesized by atom transfer radical polymerization(ATRP)and Cu(I)-catalyzed cycloaddition of alkynes and azides(CuAAC).The structure,molecular weight and molecular weight distribution of the copolymer were characterized by FT-IR?1H-NMR,GPC respectively.The thermodynamic properties?crystallinity and hydrophilicity of the copolymer were studied by TGA,XRD and the contact angle measurement,respectively.Compared with linear-PCL-b-PVP,the results showed that the thermal stability of the cyclic copolymers is obviously improved,and the hydrophilicity and crystallinity of the cyclic copolymers had also been changed.In the chapter three,the PCL-b-PVP amphiphilic copolymer micelles was prepared through the self-assembly of amphiphilic chains,then the drug Indomethacin was loaded in the micelles.We determined the critical micelle concentration(CMC)of linear and cyclic copolymer respectively using Pyrene as fluorescent probe.The results showed that the CMCs of two copolymer micelles were small,and micelles were stable.Also,we used Zetasizer Nano and TEM investigated the size and morphology of copolymer micelles.We found that the size of copolymer micelles was small and the shape of particle was spherical.Compared with the size of linear polymer precursor micelles,the size of cyclic polymer micelles was smaller because of it had no end groups on chains and so polymer chains arranged more tighter after cyclization.After loading drug,because of loading Indomethacin successfully,the size of micelles became larger.In the chapter four,the biodegradable and thermosensitive cyclic poly(?-caprolactone-b-(N-isopropylacrylamide))copolymer(cyclic-PCL-b-PNIPAM)was synthesized by atom transfer radical polymerization(ATRP)and "click" chemistry CuAAC.The structure,molecular weight and molecular weight distribution of the copolymer were characterized by FT-IR,1H-NMR and GPC,respectively.The thermodynamic properties,thermosensitity,crystallinity and hydrophilicity of the copolymer were studied by TGA,DSC,XRD and the contact angle measurement,respectively.Compared with linear-PCL-b-PNIPAM,because of the formation of cyclic topological structure with no end group,the thermal stability,crystallinity and hydrophilicity of the cyclic copolymers were obviously changed.The phase transition temperature of cyclic-PCL-b-PNIPAM was 37.5?,indicating that thermosensititve PNIPAM was systhesized successfully.In the chapter five,the PCL-b-PNIPAM amphiphilic copolymer micelles was prepared through the self-assembly of amphiphilic chains,then the drug Indomethacin was loaded in the micelles.We determined the critical micelle concentration(CMC)of linear and cyclic copolymer respectively using Pyrene as fluorescent probe.The results show that the CMCs of tow PCL-b-PNIPAM copolymer micelles were small and micelles were stable.Also,we used Zetasizer Nano and TEM studied the size and morphology of copolymer micelles.We found that the size of copolymer micelles was small and the shape of particle was spherical.Compared with the linear polymer precursor particle size of micelles,cyclic polymer particle size of micelles was smaller because it had no end groups on chains and polymer chains arrange more tighter after cyclization.After loading drug,the size of micelles became larger because of loading Indomethacin drug successfully.